All-optical, low-power modulation is a major goal in photonics. Because of their high mode-field concentration and ease of manufacturing, nanoscale silicon waveguides offer an intriguing platform for photonics. To the best knowledge and belief of the inventor, all-optical modulators built with silicon photonic circuits have relied on either two-photon absorption (TPA) or the Kerr effect. Both effects are weak in silicon, and require extremely high (˜5 W) peak optical power levels to achieve modulation.
Almeida et al (“All-optical control of light on a silicon chip,” Nature, vol. 431, pp. 1081-1084, 2004.) and Foerst et al (“High-speed all-optical switching in ion-implanted silicon-on-insulator microring resonators,” Optics Letters, vol. 32, pp. 2046-2048, 2007) have recently demonstrated an all-optical modulator with single-photon absorption-based carrier injection using visible light. This approach has severe limitations. Because of the disparate wavelengths for gate and signal, these devices cannot be cascaded into circuits that require feedback.
There is a need for an all-optical modulator that uses the same wavelength of light to control the device as is used to carry signals representing information through the device.